nx.json should support parallel as a percentage to be consistent with cli arg

Current Behavior

The docs for nx.json constrain parallel as a number.

This is inconsistent with Run Tasks in Parallel which additionally supports a percentage.

Expected Behavior

For consistency and flexibility, support both number and percentage.

The percentage is desirable in order to handle various host environments - our dev systems have way more cores than our hosted azure agents (2 cores).

GitHub Repo

No response

Steps to Reproduce

In nx.json, set "parallel": "50%" nx run-many -t build Expected:

see parallel task count equal to half the available cores Actual:

failure with error -| NX The "setMaxListeners" argument must be of type number. Received type string ('50%10')

Nx Report

Node           : 22.16.0
OS             : win32-x64
Native Target  : x86_64-windows
npm            : 10.5.0

nx (global)            : 20.0.6
nx                     : 20.8.2
@nx/js                 : 20.8.2
@nx/jest               : 20.8.2
@nx/eslint             : 20.8.2
@nx/workspace          : 20.8.2
@nx/angular            : 20.8.2
@nx/cypress            : 20.8.2
@nx/devkit             : 20.8.2
@nx/eslint-plugin      : 20.8.2
@nx/module-federation  : 20.8.2
@nx/plugin             : 20.8.2
@nx/rspack             : 20.8.2
@nx/web                : 20.8.2
@nx/webpack            : 20.8.2
typescript             : 5.7.3
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Failure Logs

Package Manager Version

No response

Operating System

• macOS
• Linux
• Windows
• Other (Please specify)

Additional Information

This was originally reported by @Tungsten78 in https://github.com/nrwl/nx/issues/31694 which I believe was unintentionally closed by @AgentEnder in https://github.com/nrwl/nx/pull/32027 which is completely unrelated.